Heater



' Jan'. 2, 1.945. H. J. DEIN. MccoLLuM 2,365,416

HEATER Filed June 5, 1943 .9W w@ Ew w% @m1, NM1. .NW Nw GJ NW QW.

atenteci Jan. 2 @d @EWE TATS PATENT' .My invention relates to heaters and more particularly to'heaters of the internal combustion type commonly usedin airplanes.

In internal combustion heaters it is common to provide a muffler to eliminate objectionable noise resultingA from heater operation and I have found that a mutller having a single open muf- Where the muffler chamber is relatively small,

it is only possible to prevent the pressure in this vchamber from rising with each irregularity in'v combustion. by maintaining a substantially free and open .communication between this mufiler chamber and atmosphere. 'y

This is ordinarily accomplished by providing relatively free ow of secondary air throughv the muier, this secondary air being discharged into the gas passages by way of the acoustic couplings between these passages and the interior of the muffler. This arrangement has the disadvantage that it materially decreases the efficiency of the heater, as the acoustic couplings between the muier and gas passages must be adjacent the combustion chamber of the heater for best results and the discharge of large quantities of secondary air into the hot gases leaving the combustion chamber materially cools these gases and decreases the heat transfer from these gases to the heat exchanger and Ventilating air.

Where the muilier chamber is made large enough so that the pressure therein will not increase materially with variations in combustion, no communication is required between this chamber and atmosphere to make it eiective as f an adequate muffler. However, such a chamber must be in communication with the gas passages through the acoustic couplings between the interior of this chamber and these passages. Un,-y der certain conditions of heater operation, a combustible mixture may accumulate in the large volume muiling chamber and if this mixture be ignited, an explosion may occur which will injure or destroy the heater. An object of my invention is to overcome these disadvantages of the large muling chamber.A v v Another object of my invention is to provide' a heater having a large muling chamber and wherein means is provided for a slow flow of air through the muillling chamber to prevent the formation of a combustible mixture therein.

Another object of my invention` is 'to provide a heater having new and improved means for preventing gasoline or gasoline vapors from entering the Ventilating air delivered by the heater 4 to the cabin or other space or spaces to be heated.

Another object of my invention is to provide a simple, inexpensive, eicient and durable heater which may be manufactured by conventional equipment and methods and which may be easily disassembled and reassembled for inspection, cleaning and repair. I

Other objects and ladvantages will become apparent as the description proceeds.

'In the drawing:

Fig..1 is a longitudinal, sectional view through a preferred embodiment of my invention; and

Fig. 2 is a' partial, longitudinal, sectional view of a modied form of my invention.,

In Fig. 1, I have shown a heater comprising a combustion chamber l@ having an annular wall l2 provided with -a :flange it attached by screws i6 to a ring i8 forming one end of a heat exchanger indicated generally by reference charac- The screws It also serve to attach the combustion chamber and heat exchanger `to brackets 22 attached to a cylindrical heater eas ing 2li by means of screws 26. The opposite end of the heat exchanger has a similar ring 28 attached to brackets 3@ by screws 32, which also serve to `secure an end platev to the ring 2t. The brackets 39 are attached tothe casing 2d by screws 36.

'I'he heat exchanger 2t is shown as being of the type described and lclaimed in my :so-pending applicatiomserial No. 464,451, filed November 4, 1942, although other forms of heat exchanger may be used in lieu thereof. The heat vexchanger shownf'comprises, in addition to the rings i8 and 28, a tubular shell 38 which is corrugated to form gas passages a and to clamp the bases of longitudinally extending ns 42 between the corru-= gations forming the gas passages. The Ifins t2 project into the annular Ventilating air passage M .formed between the shell 33 and casing 2t and serve to transmit heat tothe Ventilating a owing through this passage.

casing 2d into an airplane cabin or through a duct system having selected outlets arranged in the same or different spaces. A small portion of the heated Ventilating air enters the inlet end 48 of a combustion air pipe 59 leading to the air inlet of the carburetor 52 where it is mixed with fuel to form a combustible mixture. A pipe 54 connects the carburetor 52 with any suitable source of fuel.

The mixture of fuel and air formed in the carburetor 52 leaves this carburetor by Way of induction tube 5B, having an end 58 located in the lefthand portion of combustion chamber I0, where it is ignited by an electrical igniter 60 located in a pocket at one side of th/e combustion chamber andv communicating therewith through openings 62 and 64. A spiral c-shaped ring 66 serves to direct any liquid fuel delivered to the combustion chamber into the opening 62 for vaporization and ignition by the igniter 62. The re-igniter 68 is provided to maintain combustion after the igniter is cut out by the usual thermostatic switch. The particular structure and arrangement of the combustion chamber and its associated parts is claimed in my copending application, Serial No. 481,835, filed April 5, l1943, and my earlier applications therein referred to.

let pipe 16, an outlet fitting 18, and any suitable exhaust pipe attached to the threaded end of this fitting.

The muffler 12- is preferably formed of sheet metal and has a cylindrical wall 80 which cooperates with the shell 38 of the heat exchanger to form the gas passages 40. The rear end of this muiiier is provided with a sheetmetal Wall The walls of this muflier form a single mui-- 82. fling chamber which is acoustically coupled to the gas passages through a single annular row of openings 84 formed in the cylindrical wall 80 adjacent the head end of the muiiler. This muffling chamber'requires no stainless steel wool or glass wool, or other sound absorbing material, such as commonly provided in the mufllers used in connection with this type of heater. The capacity of this muilling chamber is sufiiciently great so that the pressure of any gas or air contained therein will not be materially increased by irregularities in combustion and the muilier will eiTectively absorb the objectionable noises resulting from heater operation.

Since this muiiler is connected through the openings 84 with the gas passages, it would be possible for unburned combustible mixture discharged from the combustion chamber to seep into the vmuiliing chamber unless special means were provided to prevent such seepage. I prevent seepage `of combustible mixture into -the muiiiing chamber by providing a slow iiowof heater efliciency by decreasing the heat transfer betwen these gases and the heat exchanger. A feature of my invention, however, lies inthe fact that in'my novel heater much less secondary air is discharged into the combustion gases than is required by the usual heater so that the operating efficiency of my heater is not appreciably impaired by the discharge of secondary air into the products of combustion.

A small diameter pipe 86 is secured to the rear wall 82 of the muffler and projects through the plate 34 which closes the righthand end of the heat exchanger. This pipe is in open communication with the righthand end of the casing 24 so that ventilating air can flow through this pipe into the interior of the muiiier 12. Since my heater is so designed that only a very small quantity of air flows through the muler, under some conditions of operation gasoline fumes might nd their way into the Ventilating air unless special means were provided to prevent such an occurrence. I shall now describe this special means. l The pipe 88 is provided with a restriction 88 and also with an annular series of openings 90 which connect the interior ofthe pipe on the muiiier side of the restriction 88 with the outlet chamber 14. The restriction 88 provides a relatively small opening through which the air flows rapidly so that no gasoline fumes can pass through this opening into the Ventilating air. l'n order, however, to create the desired rate of flow through the restriction 88, it is necessary to pass more air through this restriction than it is desirable to discharge into the gas passages 40 as secondary air. The openings 90 permit most of the air flowing through the restriction 88 to pass into the outlet chamber 14 where it performs the desirable -function of diluting the gases in this chamber and in the exhaust system connected therewith sumciently to prevent combustion therein. The air passing from the tube v86 through openings 90 and into outlet` chamber 14, however, has no eiect on the eiiiciency of the heat exch'anger and only an extremely small quantity of air is discharged into the gas passages 40 through the `openings 84. The 'air ow through the muier is extremely slow and just suiiicient to prevent the 'accumulation of an explosive mixture therein.

Because the flow of air through the muffler is very slow, this air flow has little cooling effect on the head end of the muffler which is exposed to the'heat of the combustion chamber and the hot gases issuing therefrom. In some sizes and designs of heater this heat will not be sufficiently intense to injure the head end of the muffler, whereas in other designs it is desirable to pro- `tect the head end of the muffler by a layer of insulating material, as shown in Fig. 2. In this figure, a disc I 00 is attached by screws |02 to the end wall 10 which corresponds to the end wall 10 of the embodiment of Fig. 1.

My novel heater may be madeOf conventional materials and by conventional equipment and methods. The various parts of the heater are of rugged construction capable of affording long y 1. A heater of the class described, comprising*- a casing having one end adapted for connection 5 to a source of air, a combustion chamber in said casing, a heat exchanger connected to said combustion chamber and receiving hot products of combustion therefrom, a muiiier located in said heat exchanger and having a head end adjacent said combuston chamber, said muiiier having a large muiing chamber, openings in the head endv of said muiler forming acoustic couplings between said muiiiing chamber and said combustioir chamber, means providing an oriiice connecting the other end of said muiiiing chamber with the interior of said casing, and means interposed between said orifice and said mufing chamber for diverting to an exhaust outlet most of the air passing through said orifice before reaching said muiliing chamber.

2. A heater of the class described, comprising a combustion chamber, a mufller for absorbing sound created by combustion in said chamber, said muler having a muilling chamber, a heat exchanger receiving (hot products of combustion from said combustion chamber, means -for directing Ventilating air over said heat exchanger, means including openings connecting said muf- Iier wth said combustion chamber and with the ing excess air passing through said last-named opening.

3. A heater of the'class described, comprising a casing connected to a source of Ventilating air, av heat exchanger in said casing, a combustion l chamber connected to said 4heat exchanger and deliveringhot gases thereto, a muiiler having a xnuiliingl chamber, means -providing openings l forming .acoustic couplings between said chambers and permittingy ow` of secondary' air from said muiiiing chamber into hot products of combustion from said combustion chamber, means including an orice connecting. said. muiliing chamber with the interior off said casing, means for causing more, air toowthrough said orifice than enters said muming chamber, and means for exhausting excess air owing through said orice.

4. A heaterof the class described, comprising a casing having an end adapted for connection tov a source oi' air supply, a combustion chamber, a

heat exchanger in said casingreceiving hot gases s from said combustion chamber, a mumer vhaving a muming chamber, means forming an. acoustic coupling between said muiiiing chamber' and said combustion chamber, said means affording open `communication between said chambers, a-pipe connecting said muiiiing chamber with the interior of said casing whereby air can ow from said casing into said muiiiing chamber, means including an opening intermediate the endsof said pipe for causing more air to enter said pipe than is discharged by said pipe into said muling' chamber, and means `forexhaustingexcess air entering said pipe.v

5. A heater of the class described, comprising a casing having one end connected to a source of air, a heat exchanger located in said casing and n having gas passages therein, means for supplying hot gases to said passages, a mufer located in said heat exchanger, said muilier providing a muffiing chamber, means providing an acoustic coupling between one end of said chamber' and said passages, said means permitting fluid ow between said passages and muiiling chamber,

means providing an outlet chamber in :communi-A cation with said gas passages, a pipe extending throughsaid outlet` chamber and connecting said muflling chamber with the interior of said casing,

and an opening in said pipe Vfor diverting into said outlet chamber part of the air entering said pipe from said casing. l

6. A heater ofl the class described, comprising a casing connected toa source ofgair, a combustion chamber, aheatjexchangerilocated in\said casing and receiving hot gases from said com-v A bustionchamber, said heat exchanger having gas y passages therethrough, amuilier located in said heat exchanger and having a muiiifngchamber,

means providing an acoustic coupling between said muilling chamber and one end of said pas-'- sages, tubular means for admitting air from said casing t0 said muiilingchambenand means com 40 nectin'gan intermediate portionl of said tubula member with the outlet end of said gas passages. '1. A heater of the class described, comprising a casing adapted for connection to a source of air,

la combustion chamber in said casing, a heat-exchanger connected to said combustion chamber, a

'muiier associated with saidheat exchanger, said 'muilier having a head end exposed to heat from said combustion chamber.- insulating means for said end, acoustic 'couplings` adjacent said end.

and means for gcausing secondary airl to ow' through saidcouplings, said means comprising a connection between the other end of said mufiier and the' interior vof said casing, means for causing more-air to iiow through a part of said connection than is delivered to said muiiler, and means` for exhausting excess air flowingthrough Said part.

HENRY?. DENT- MCCOLLUM. 

